Celecoxib forms crystals when diluted in RPMI how do I avoid this - (Jun/21/2013 )

I need to dose my cells with celecoxib so I made a stock solution of 25mM with 100%DMSO as recommended. It was well dissolved. I further diluted it to 10mM and 1mM before my final concentration of 100uM but it forms a lot of crystal and I can see a lot of crystal in the assay. Also I think this affect the acvtivity of the drug. Can anyone advise on this please. Thanks

-Peniel-

you can add a little more dmso to the rpmi (if the system can tolerate it).

did you perform your initial dilutions with rpmi or dmso?

-mdfenko-

The 10mM and 1mM were diluted in RPMI. The crystals were initially formed in the 10uM stock.

-Peniel-

HELLO if you sonicat your rpmi with your drug perhaps is usefull

-antitoxin-

Dont make the intermediate dilution. Add the desired amount of 25mM stock to the RPMI, mix and look for precipitate. Only add extra DMSO to the final solution if needed, no need to overcomplicate things. I think 100 uM should be OK, but you won't be able to go much higher.